This video shows you how to make rich chocolate butter sandwich cookies, inspired by the chocolate butter sandwich cookies from a famous shop. First, cream together unsalted butter and granulated sugar, then mix in beaten egg, cake flour, and pure cocoa powder to make cookie dough, and let it rest in the refrigerator for a long time. Roll out the dough thinly, cut it into rectangles, and bake it in the oven. Next, prepare chocolate buttercream made with unsalted fermented butter and powdered sugar, and ganache made with heavy cream and chopped dark chocolate. Mix the ganache into the chocolate buttercream, pipe it onto the baked cookies, add a little ganache, and sandwich with another cookie. Finally, chill in the refrigerator until firm, and you'll have delicious chocolate sandwich cookies that are perfect as a Valentine's Day gift.